Airfoils used in aircraft engines, such as fan blades of a gas turbine engine, can be susceptible to extreme loading events. For instance, a fan blade might strike a bird that is ingested into the engine, or a blade-out occurrence may arise wherein one of the fan blades is severed from a rotor disk. If the impact is large enough, a fan blade may break apart into one or more shards before traveling downstream through the engine.
Gas turbine engines, such as turbofans, generally include fan cases surrounding a fan assembly including the fan blades. The fan cases are generally configured to withstand an impact of the fan blades due to adverse engine conditions resulting in a failure mode, such as foreign object damage, hard rubs due to excessive or extreme unbalance or fan rotor oscillations, or fan blade liberation. However, such airfoil configurations generally increase the weight of the fan case, thereby increasing the weight of the engine and aircraft and reducing performance and efficiency.
Known fan cases generally include frangible structures, such as honeycombs or trench-filler material, configured to mitigate load transfer to and through the fan case. However, this approach is generally costly. Furthermore, this approach may result in larger, heavier, less efficient fan cases. Still further, this approach may not address issues relating to fan rotor unbalance following deformation or liberation of one or several airfoils such as fan blades.
As such, there is a need for an airfoil that enables a controlled and consistent failure mode of the airfoil that may enable reducing a cost, weight, and load transfer to a surrounding casing.